Oxidizing preparations are used for decoloring and bleaching hair. These preparations usually comprise a bleaching powder (powder mixture of inorganic persalts, e.g. sodium or ammonium persulfate, with) on the one hand and an aqueous hydrogen peroxide solution on the other hand.
During application, the bleaching powder is stirred with the aqueous hydrogen peroxide solution. In so doing, a cream or paste which is capable of being applied and is not runny is obtained due to the contained thickening ingredients. The formulations must have a pH value between 8 and 11.5, preferably between 9 and 10, to effect a sufficient bleaching action.
Since commonly used hydrogen peroxide solutions are adjusted so as to be strongly acidic for the purpose of stabilization, the bleaching powder contains a large proportion of alkaline reacting, e.g. sodium carbonate or sodium silicate. When mixing bleaching powder and peroxide solution the pH value is adjusted to the desired range on the one hand due to the and ammonia is released from the ammonium salts contained in the formulation on the other hand, which ammonia causes a swelling of the hair and accordingly a strengthening of the bleaching action.
However, these preparations for producing bleaching agents in the form of powder mixtures have grave disadvantages. For example, separation can occur when using components having different densities because the heavy particles can deposit on the lower portion of the container when transported or stored. As a result, the powder removed from the bottom portion does not have the same chemical composition as that removed from the top portion and has a different bleaching effect.
Separation can be avoided to a great extent through the use of powder mixtures with very small grain sizes. However, these fine powders have the disadvantage that they tend to develop dust extremely easily. Dust develops particularly when opening the container, but to an even greater extent when removing the required amount, which is usually accomplished with a measuring spoon, and also when agitating the ready-to-use formulation. The release of fine dust can lead to irritation of the respiratory organs, particularly as a result of the utilized persulfates. Further, the powder mixtures have a large surface as a result of the small size of the particles, which can lead to a higher absorption of moisture when opening and closing the container and to a deactivation of the bleaching action.
To solve this problem it is suggested in DE-OS 20 23 922 to change the components of the powder mixture into granule form with a water-soluble polymer. As described in DE-OS 20 23 922, this method leads to a loss of ammonia when using aqueous solvent for the polymer. To compensate for this loss it is suggested to increase the content of ammonium salts in the powder mixture. Of course, the loss of ammonia during technical production of the described granules is very difficult to keep constant, so that the chemical composition of the granules produced according to this method fluctuates.